Learn Hardcore Polish: Mój pociąg odjeżdża z peronu drugiego.

Because the preposition z (from) governs the genitive case. peron in genitive singular is peronu, and the ordinal drugi must agree with that case and gender, becoming drugiego. Pattern: z + GEN (e.g., z lotniska, ze stacji, z mostu).

Can I also say z drugiego peronu? Is there any difference?

Yes. Both z peronu drugiego and z drugiego peronu are correct and mean the same. z drugiego peronu is more everyday/conversational; z peronu drugiego sounds a bit more formal or announcement-like.

Why present tense odjeżdża if the departure is in the future?

Polish often uses the present tense of an imperfective verb for schedules and timetables: Pociąg odjeżdża o 8:00 = The train leaves at 8. If you want to stress a one-off future event, you can use the perfective future: Pociąg odjedzie o 8:00.

What’s the nuance between odjeżdża, odjedzie, wyjeżdża, and can I say odchodzi?

odjeżdża (imperfective): default for train departures; schedules or an action in progress.
odjedzie (perfective future): a single future departure.
wyjeżdża: general “leaves/drives out”; acceptable but less rail-specific.
Avoid odchodzi for trains in modern usage; it usually means “walks/goes away” and sounds odd here.

Why z and not od for “from the platform”?

Use z + genitive for movement away from a place. od is “from” a person/source or “away from” relative to an object. Pociąg odjeżdża od peronu would describe the train moving away from the platform, not departing from platform 2 as its scheduled point of origin.

Is peron the same as tor? Which should I use?

peron = platform (where passengers stand).
tor = track (the rails). In everyday speech, z peronu drugiego is standard. Official announcements may specify both: z toru drugiego przy peronie drugim.

How do I ask “From which platform does the train depart?” in Polish?

Say: Z którego peronu odjeżdża pociąg do …? The preposition z requires genitive, hence z którego.

How do I say an arrival to a platform?

Use na + accusative: Pociąg przyjeżdża na peron drugi (arrives at platform two). Departures use z + genitive: odjeżdża z peronu drugiego.

Why Mój and not Moja/Moje? What gender is pociąg?

pociąg is masculine inanimate, so the nominative singular possessive is mój. Feminine would be moja, neuter moje. Example: moja walizka (my suitcase), moje miejsce (my seat).

Can I drop mój?

Yes, if the context makes it clear. Pociąg odjeżdża z peronu drugiego is natural when it’s obvious which train you mean.

Any pronunciation tips for the whole sentence?

pociąg: ą before g sounds like nasal “ong” (approx. POH-chyonk).
odjeżdża: dż like English j in judge; rz sounds like ż (zh). Approx. od-YEZH-jah.
z peronu: z devoices to [s] before p, so it sounds like “s peronu”.
drugiego: hard g (dru-GYE-go). Polish stress falls on the second-to-last syllable.

Why drugi/drugiego (ordinal) and not dwa/dwóch (cardinal)?

Platform numbers are usually expressed with ordinals as attributes: peron drugi / z peronu drugiego. Cardinals (dwa/dwóch) count items, not label them. On signs you’ll also see digits: peron 2.

Can I write it with a digit? Any common abbreviations?

Yes: Mój pociąg odjeżdża z peronu 2 or … z peronu nr 2. In speech, prefer peronu drugiego or peronu numer dwa/drugi; peron dwa is heard but feels telegraphic.

Is there any difference between Pociąg mój and Mój pociąg?

Mój pociąg is the normal order. Pociąg mój is rare/poetic or used for special emphasis on the noun.